Agricultural tractors are increasingly being equipped with suspended front axles. Thus John Deere offers, under the name “TLS” (Triple Link Suspension), a hydraulically sprung floating axle, which is pivotably suspended by a trailing arm on a chassis of the agricultural tractor and which is supported on the chassis of the agricultural tractor by means of two hydraulic struts opposing one another in the transverse direction. Each of the two hydraulic struts has a hydraulic cylinder and a hydraulic piston that subdivides the hydraulic cylinder into an annular space and a piston space. A hydraulic controller connected to the two hydraulic struts makes it possible to regulate the level of the chassis of the agricultural tractor in relation to the ground by appropriate application of pressure to the piston spaces. In addition, a plurality of diaphragm accumulators communicating with the hydraulic struts are used to implement a spring function, wherein the spring stiffness of the hydraulic struts can be varied by the hydraulic controller by applying appropriate pressure to the annular spaces. The extent of the pressure application is monitored by means of a pressure sensor that communicates with the annular spaces.
The varying pressure conditions as a result of the hydraulic level or spring stiffness regulation complicate an assessment, by means of the pressure sensor, of the axle load acting on the front axle. Exact knowledge of this load is necessary, however, for purposes of an adaptive control of the running gear or for automatically operating a central tire inflation pressure system for the agricultural tractor.